This invention relates to pressure responsive devices for use in automobiles, tractors and other heavy equipment and the like for performing a control function in response to the occurence of selected pressure levels in the equipment during equipment operation. The invention relates more particularly to pressure responsive devices which are subjected to relatively high hudraulic pressures in automobile applications and the like and which are adapted to be reliable and to display long service lives in such applications.
Conventional pressure responsive devices have control components such as electrical contact means which are movable to perform control functions when selected levels of pressure are applied to the devices. Many of such devices incorporate a metal disc or diaphragm having a flange for use in mounting the diaphragm and having a domed central portion which is movable from an original dished configuration toward an inverted dished configuration when a selected fluid pressure is applied to the diaphragm. The snap acting movement of the domed disc portion causes sharp movement of the electrical contacts or other control components between the noted control positions, and the characteristics of the disc determine the actuating pressure at which such movement occurs. The disc diaphragm also serves to seal the device against fluid pressures in the zone being monitored. In many conventional devices which are intended for use in high pressure zones, a support engages the disc when the disc has moved into its inverted dished configuration for preventing excessive movement of the disc to avoid disc rupture. However, it is frequently found that, when such devices are subjected to relatively high levels of applied pressure, the devices tend to have relatively short service lives even though the device proportions have been increased to display greater strength. In this regard, it has been found that the disc diaphragms have tended to be subject to fatigue cracking in high pressure applications, particularly at the locations where the domed disc portions join the flange parts of the discs.
It is an object of this invention to provide a novel and improved pressure device and to provide such a device which is adapted to display improved reliability and service life even when used in high pressure applications.